I’m trying to edit thank you page by overwriting template files

I want to customize the thank you page so I can add some data to the data layer.

So, I am wanting to customise the thank-you.php.

For some reason when I set up my child-theme and want to paste the thank you page into the folder environment:

childthemeFolder > woocommerce > checkout > thankyou.php

However, when i customise the thankyou.php within the childtheme environment none of the changes takes effect. it still defaults to the original file located in the plugins > woocom > templates > checkout > thankyou.php

Can anyone advise me why this is happening and how to fix it please?

Thanks so much.

The page I need help with: [log in to see the link]